I definitly think Fred shouldn't have turned her back on him. If necassary, she should have joined him and left the others, but I think I would have liked if she had been in both "teams". Working with Wesley on some cases, or just being there for him, while still doing her job at Hyperion with the others, trying to get them to forgive Wesley.
I get why Angel did it (obvious reason) and everyone else except for Cordy and Fred. Gunn and he wasn't that close anymore, because of Fred and because Gunn didn't like the coldness he saw in Wesley in Pylea(I'm guessing), but I still think he should have payed a visit. He always seemed ready to slay Angel if Angelus ever came back, so why shouldn't he get why Wesley did what he did when he thought Angel would go bad? But
let's blame it on the jealousy and that they weren't that close.
However, Cordy has no excuse. Sure, she was probably in love with Angel by then and loyal to him the most, but she, Wesley and Gunn only had each other the year before, and she doesn't even visit Wesley? She said that Angel needed her and she picked sides or whatever, not caring about what that did to Wesley. I don't even think they have any friction going on in season 4. Could be because Cordy was Jasmine possessed, hence not feeling as hurt as Fred and Gunn who at least made some scenes showing their hurt over Wesley's "betrayal".
So yeah, a scenario like you describe might have been good, because I think it would have been dealt with better. I really don't get why in the end, Angel is the only one that actually says that he understood what Wesley did (Ground State
http://vrya.net/bdb/clip.php?clip=4799)
But in this version, we did get one of Wesley's most awesome scenes/lines (Spin The Bottle)
"WESLEY: Do you think you could get out of my way? (puts up his right hand to push Gunn away)
GUNN: (grabs Wes's hand) I don't know what—
WESLEY: (a blade springs out of his forearm contraption) Not all of us have muscle to fall back on. (retracts blade and walks away)
GUNN: What happened to you, man?
WESLEY: I had my throat cut and all my friends abandoned me."
That last line makes me shiver every time. That's good writing. And then there's dark Wesley, which we wouldn't have had in case the others had forgiven him too quickly.
I guess you could say that in the aired version, I learned to appreciate Wesley more, but dislike the others. In your scenario, I would like the other characters more, but I'd never gotten to see depressed dark Wesley (who even though he was abandoned, did so much for his former "friends")who's one of the good things about season 4.